Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a first image in sequence for a display screen or portion thereof with transitional graphical user interface, showing our new design;

FIG. 2 is a front view of a second image thereof;

FIG. 3 is a front view of a third image thereof; and,

FIG. 4 is a front view of a fourth image thereof.

The broken lines within the figures show unclaimed portions of the transitional graphical user interface, and the broken lines around the figures showing of the display screen are included for the purpose of illustrating environment structure; the broken lines form no part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-4. The process or period in which one image transitions to another image forms no part of the claimed design. 

CLAIM We claim the ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 